June 11, 2010 -- Avastin improves vision for people with the wet form of age-related macular degeneration (AMD), a U.K. study suggests.

That's no surprise to the 60% of U.S. doctors who already use tiny doses of the cancer drug instead of the vastly more expensive Lucentis.

What remains frustrating is that until a U.S.-funded study is finished next year, nobody knows for sure whether Avastin works as well as or better than Lucentis for AMD -- or which patients, if any, would benefit more from one drug than from the other.

Both Lucentis and Avastin inhibit a molecule called vascular endothelial growth factor or VEGF. Avastin is a humanized monoclonal antibody. Lucentis is largely the same antibody pruned down to its active fragment and enhanced for greater anti-VEGF potency.

When injected into the eye with a tiny needle, both drugs stop the inappropriate growth of blood vessels that leak fluid and displace the retina. Both drugs are made by Genentech, now owned by Roche. But the similarity ends there.

Avastin is not an FDA approved treatment for AMD. Genentech is not seeking such approval and does not make the drug in the tiny dosages needed for AMD treatment.

A compounding pharmacy, however, can break down a vial of Avastin into AMD dosages for about $20 a dose. The cost of a dose of Lucentis is about $2,000. This 100-fold cost difference is why so many ophthalmologists are using Avastin for AMD, even though it is not an approved use of the drug.

Now Adnan Tufail, MD, of Moorfields Eye Hospital, London, and colleagues have demonstrated in a clinical trial that Avastin does indeed improve vision in patients with AMD. This supports the use of Avastin -- but does not answer the question of whether it is the best treatment.

In an editorial accompanying the Tufail study, Usha Chakravarthy, MD, PhD, of Ireland's Royal Victoria Hospital, notes that the findings will reassure doctors who treat AMD patients with Avastin.

However, she concludes that "off-label use of [Avastin for AMD] should not be encouraged until the large randomized trials comparing it with [Lucentis] report their findings."

There are six such trials under way. The U.S. trial, funded by the NIH, is furthest along. Results are expected in early to mid-2011.

"Until then, clinicians have already decided which drug they prefer in the U.S., " researcher Philip J. Rosenfeld, MD, PhD, professor of ophthalmology at the University of Miami's Bascom Palmer Eye Institute, tells WebMD via email. Rosenfeld has conducted clinical trials of Lucentis and also has pioneered the use of Avastin for AMD.

Some doctors, Rosenfeld says, use Lucentis because they can recover 6% of the average sales price if they sell the drug to their patients. Others prefer Avastin because they are at less risk if a patient's insurance company refuses reimbursement. Genentech, he notes, is in no hurry to get Avastin approved because the company makes nearly $1 billion a year on Lucentis sales in the U.S. alone.

Financial incentives, of course, are a poor way to decide which drug to use. There's reason to believe that Lucentis works better, because molecule for molecule, it's a stronger inhibitor of VEGF than is Avastin. But there's also reason to think Avastin works better: It's a larger molecule that may linger longer in the eye, reducing the number of uncomfortable injections needed each year.

In past interviews, retina specialists have told WebMD that some patients do better on Avastin, while others do better on Lucentis.

In all cases, however, the treatment only works for patients treated in the first year wet AMD develops. In later stages of AMD, there is irreversible damage to the retina.

It's also not clear how often patients need Avastin or Lucentis injections. Some patients appear to require monthly injections, while others need no more than two a year.

The Tufail study, and the Chakravarthy editorial, appear in the June 11 online edition of BMJ. Rosenfeld has received study grants and speakers fees from Genentech and/or other pharmaceutical companies. He has publicly argued that the cost of Lucentis is too high.